Surgical intervention at damaged or compromised bone sites has proven highly beneficial for patients, for example patients with back pain associated with vertebral damage. Bones of the human skeletal system include mineralized tissue that can generally be categorized into two morphological groups: “cortical” bone and “cancellous” bone. Outer walls of all bones are composed of cortical bone, which has a dense, compact bone structure characterized by a microscopic porosity. Cancellous or “trabecular” bone forms the interior structure of bones. Cancellous bone is composed of a lattice of interconnected slender rods and plates known by the term “trabeculae.”
During certain bone procedures, cancellous bone is supplemented by an injection of a palliative (or curative) material employed to stabilize the trabeculae. For example, superior and inferior vertebrae in the spine can be beneficially stabilized by the injection of an appropriate, curable material (e.g., polymethylmethacrylate (PMMA) or other curable material). In other procedures, percutaneous injection under computed tomography (CT) and/or fluoroscopic guidance of stabilization material into vertebral compression fractures by, for example, transpedicular or parapedicular approaches, has proven beneficial in relieving pain and stabilizing damaged bone sites. Other skeletal bones (e.g., the femur) can be treated in a similar fashion. In any regard, bone in general, and cancellous bone in particular, can be strengthened and stabilized by a palliative injection of bone-compatible curable material.
The curable material used in the above procedures is typically fashioned by mixing a liquid component and a powder component within the operating room just prior to placement of the curable material into an injector wherein the injector is then used to introduce the curable material into the patient. Curable material may be prepared by mixing a very fine cement powder, typically PMMA, with a liquid monomer, typically methylmethacrylate.
According to mixing methods of the prior art, the components of the curable material are mixed in a mixing bowl and then transferred to a delivery system, such as a syringe or other injector, to deliver the curable material to the patient. This method can delay procedures while the cement is being transferred to the delivery system and the curable material may be spilled during the transfer. The delay increases procedure time and can cause the curable material to set before the procedure is completed. Additionally, the mixing of the components creates undesirable fumes that have an offensive odor to many. The mixing of the components in an open mixing bowl exposes the operating room to obnoxious fumes. Further, mixing is typically done by hand by the physician. Hand mixing can be tedious and unpredictable, resulting in potentially poor quality curable material.
Additionally, after the curable material has been mixed and transferred to the delivery system, the curable material typically becomes increasingly viscous as time passes. Increased viscosity requires higher loads to be applied to the curable material in order to force it to flow through a delivery cannula. Internal chamber pressures can typically be 1000 psi to 4000 psi or more. Additionally, the required axial load to drive curable material from a chamber is equivalent to the chamber pressure multiplied by the cross sectional area of the chamber. As a result, chambers having a relatively large cross-sectional area create even higher axial load requirements on the injector device.
There exists a need in the medical device field for an improved curable material mixing and delivery device. The present invention provides an efficient device and method for mixing and delivering components of a curable material.